The invention concerns tools for turning, and especially tools for fashioning deep and/or hollow work in materials such as wood, plastics, soft metals and alabaster.
In recent years there has been a resurgence of interest in the art and craft of wood turning, including a particular interest in producing larger vessels of both the "deep" and "hollow" types. Usually the term deep refers to a cavity the internal diameter of which decreases progressively from the mouth to the bottom of the cavity. A simple example is an open cone. The term hollow refers to vessels in which there is at least one internal chamber with a mouth or entrance of smaller diameter than the maximum internal diameter of the chamber. A simple example is a sphere with a circular opening.
Two of the problems facing the turner desiring to fashion deep or hollow vessels significantly larger than those feasible and economical with conventional tools, are the volumes of material to be removed and the much greater reach of tool required. Typically these attempts at larger vessels have been made using somewhat makeshift adaptations of conventional methods and tools. The conventional way of removing redundant material is by comminution (reducing all of the material to shavings or sawdust) for example with a gouge tool. The rough forming of an extra large vessel in this way can be very laborious, time consuming and wasteful of the raw material. (Doubling the principal dimensions of a vessel increases its volume and hence the volume of material to be worked eight times.)
The second problem is the control of tools at the greater reaches involved in fashioning the inside of larger vessels. With the cutting edges of the tool more remote from the tool rest it becomes more difficult to control the tool for accurate work. A simple lengthening of the tool handle may help in holding the tool against the greater leverage resulting from increased tool reach. But typically no provision is made for holding the tool against the increased torsion forces experienced at the tool handle, especially when an offset tool is used.
A conventional tool such as a round nosed scraper may be used in a "slicing" operation to remove some volume of material, as for example in removing a cone from the end of a workpiece at the beginning of fashioning the internal form of a vessel. But the width of such tools (typically about one inch wide) wastes much material in the cuts and the operation is time consuming and inefficient.
With conventional tools, usable reach beyond the tool rest is typically of the order of two to three inches. With some adaptation greater reaches are possible, but usually only in a fatiguing operation without satisfactory control or efficiency.